


Sanster Week 2021

by DoubleSunday



Category: Undertale (Video Game)
Genre: Double Drabble, Drabble, Drabble Collection, M/M, Quadruple Drabble, Sanster, Triple Drabble, W. D. Gaster Is Not Related to Papyrus and Sans
Language: English
Status: Completed
Published: 2021-03-04
Updated: 2021-03-06
Packaged: 2021-03-17 01:20:47
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 7
Words: 2,000
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29833845
Author URL: https://archiveofourown.org/users/DoubleSunday/pseuds/DoubleSunday
Summary: Just a little collection of drabbles for Sanster week :)
Relationships: W. D. Gaster/Sans
Comments: 16
Kudos: 19





	1. Interesting Results

“So of all the places we could have gone, you wanted to come to Waterfall?” Gaster asked with a judging tone as he looked at Sans.

The skeleton put his hands in his jacket, he was nervous but it didn’t show past his smile, “Yeah, there’s a spot around here that I wanted to show you, thought you might like it.” Sans came to a stop as he finally noticed that Gaster was falling behind him, ‘You don’t like Waterfall?”

The doctor was busy trying to dodge the puddles on the floor but looked up to give Sans a frown, “What gave you that idea?”

“It’s just some water doc.”

The doctor frowned.

“Fine, it’s up ahead anyways.” Sans began to walk at a slower pace so that Gaster wouldn’t be left behind.

The two of them came to the next room, the ceiling was glittering beautifully with gems. Gaster stared up in awe at the roof.

“Not too bad for Waterfall, huh?”

Gaster looked down at Sans who smiled back at him, “No, I suppose not.”

They stayed in the room for a while talking.

“When we finally leave this place, I’m going to show you real stars Sans.”

**Notes for the Chapter:**

> Interesting results-  
> Gaster wasn't expecting to find a reason to like waterfall


	2. Lab

“Sans, could you hand me that wrench?” Gaster said waving his hand behind him, he was currently working on a machine.

“Doc, I think you need to take a break…” Sans said, putting down two cups of coffee for himself and Gaster. 

Gaster hit his head on the machine as he got up in a hurry to look at his assistant, he held his head in pain as he looked at Sans, “Excuse me?”

“You need to take a break doc.” Sans said with more confidence in his voice as he looked Gaster in the eyes, “You’ve been working on this for hours now.”

“I’m so close though Sans.” 

“That’s what you said two hours ago.”

“But I just-”

“You need a break doc, when’s the last time you slept?”

Gaster’s eye’s shifted to the side as he slightly blushed, if only Sans had known how long he had actually been working on this machine.

Sans walked up to Gaster and took his hand, Gaster looked at him in shock as the blush worsened, “Come on doc, let’s just take a quick break.”

Gaster cracked as he looked at Sans smiling softly at him.

“Fine, let’s take a break then.”

**Notes for the Chapter:**

> Lab-  
> just a normal day for Sans and Gaster


	3. Dark

“Ok Papyrus, I think it’s bedtime.” Sans proclaimed as he got up from his seat on the couch, “Gaster and I have work in the morning so we have to go to bed early.”

Papyrus got up from the ground where he was playing with Gaster, “OH… OK BROTHER!”

Papyrus got up in a hurry and scrambled up to his room to get changed into his pajamas, Sans turned to look at his coworker who was getting up from his spot on the floor.

“You really don’t mind taking the couch doc?” Sans asked, “I could always let you take my bed.”

“This is your house Sans, I will be fine.” Gaster smiled at him.

“Alright, I’m gonna go read Papyrus his story and then head to bed, you alright with me turning off the lights now?” Sans asked, walking towards the staircase.

Gaster’s breath caught for a moment but he quickly recovered, “Whatever works for you my friend.”

Sans smiled back and then shut off the lights as he walked up to Papyrus’ room, once the door closed the smile faded from Gaster’s face. He was alone, in an unfamiliar place, in the dark. This was already beginning to be a problem, he could feel the darkness creeping up around him, threatening to drag him into the shadows. He tried shutting his eyes but it didn’t work, the darkness was still all around him and his breathing became labored as he began to curl into himself. He felt like he was going to pass out when he felt a hand on his shoulder, he uncurled in a panic only to see Sans looking at him.

“You ok doc?” Sans asked.

“I’m fine, I just…” Gaster looked away from Sans, “I don’t like the dark very much.”

“Anything I can do to help?”

“No.” Gaster blushed, “Well yes, but I couldn’t ask that of you.”

“What is it?”

“Could you…” Gaster blushed harder, “Could you sleep with me tonight?”

Sans stayed silent for a short moment.

“Come on.” Sans held out a hand for Gaster, “The couch isn’t big enough for the both of us.”

Gaster's face was radiating heat but he took Sans’ hand and followed the small skeleton up to his room. The two of them settled down in the bed and Gaster smiled, he didn’t feel scared anymore with Sans by his side.

“Goodnight Sans.”

“Goodnight G.”

**Notes for the Chapter:**

> Dark-  
> Gaster doesn't like the dark


	4. Memory

‘DONT FORGET’

That simple phase haunted Sans’ mind after every reset. It was a reminder of what had happened to him in every reset, everything that the human had done to him and the people he loved. It reminded him of what could be, the perfect ending where they get to go back to the surface. Most importantly it reminded him of someone that he lost a long time ago, someone that he would never get back.

Dr. W. D. Gaster.

The man that kept him going, the one that haunted his nightmares, the one that he couldn’t save, the reason why he would never truly be happy. 

Sans took out the picture that he held on his person, it was a picture of him and Gaster right after the core had been completed. That day was such a happy day for them, all their work had finally amounted to something and paid off in full. Sans remembered how Gaster hugged him when the core powered up and began to pump out power to the underground, he remembered how natural it felt to be held in the doctor’s arms. He remembered the scent of coffee that seemed to radiate off Gaster’s person, the man did love his caffeine. He remembered the look of pure joy on Gaster’s face as the taller man shouted about how happy he was. He remembered the blush that came across his face as Gaster held him.

Sans put the photo away in his jacket pocket, where it belonged, as he turned his head upwards to stop the tears that were threatening to fall from his eyes. He wiped a small tear from the corner of his eye and let out a deep breath.

“I’m sorry Gaster, I know you wouldn’t wanna see me like this.”

**Notes for the Chapter:**

> Memory-  
> Sans reminisces with one of his pictures


	5. Warm

“Gaster is this all really necessary?”

Sans was huddled up in blankets with Gaster, he sat in the other man’s lap as they sat in front of a fire. Gaster pulled Sans into a hug and rested his head on the smaller’s shoulder as he let a small smile come to his face.

“I don’t have the same privileges as you when it comes to body heat, or lack thereof.” Gaster said softly.

“My bones are always cold, why do you want me in here with you if you want to get warm?”

“I like having you around.”

Sans stayed silent as his breath hitched, he began to blush slightly as he leaned into Gaster’s hug

“You’re lucky I like you G.” Sans leaned his head against Gaster’s.

“That I am Sans.” Gaster said kissing Sans on the side of his face, “I’m the luckiest monster in all of the underground.

“Oh shush you big softy.” Sans rolled his eyes, “I’m not that special.”

“Yes you are.” Gaster snuggled closer, “You’re the most beautiful monster in the underground.”

Sans blushed harder, this was definitely the hottest that Sans has ever remembered being. This was definitely one way to get warm.

**Notes for the Chapter:**

> Warm-  
> Sans and Gaster get warm


	6. Cold

“Couldn’t you have picked somewhere hotter to live?” Gaster asked, rubbing his hands together then breathing into them in an attempt to heat them. He and Sans were currently walking through Snowdin from the shop in an attempt to get to Sans’ house.

“It’s cheaper to live here.” Sans said, shrugging.

“Cheaper does not mean you should pick it…”

“When you gotta little brother to raise, it does.”

Gaster frowned slightly, he didn’t like it when Sans brought up that he had been the only one raising Papyrus since the skeleton's parents weren’t around. It reminded him of what Sans must have gone through during his life, it made him feel sorry for the skeleton.

“I don’t know anything about raising a child, but if you ever need help you know I’ll always be there for the two of you.”

Sans stopped for a moment, he’s never had someone other than Papyrus worry about him.

“Thanks Gaster, that really means a lot to me that you’d care about us.”

“Of course my friend, I care very deeply for both of you.” Gaster smiled, his cheeks began to sting from the blush that came to his face, “Now let’s get back.”

**Notes for the Chapter:**

> Cold-  
> Gaster doesn't like the cold, but he likes Sans


	7. AU

“I can fix everything Sans, you just have to let me go!” Gaster cried out from behind the closed door.

“Sorry doc, we don’t need things fixed.” Sans said, scratching the side of his face.

“What are you even saying!?” Gaster shouted, “Have you gone so insane that you see nothing wrong with what’s going on?”

“There’s nothing wrong here doc.” Sans leaned his head against the door, “We’ve got everything under control down here.”

Gaster slumped against the door and fell to his knees, “Sans, you’re eating humans… You can’t tell me that there isn't anything wrong with that.”

“It’s not my fault the Queen’s crazy, besides…” Sans got up from his spot on the floor, “I don’t do that crap.”

Gaster stayed silent, closed his eyes, and he let out a deep breath as he heard footsteps leaving from the other side of the door. He opened his eyes only to notice that there were now a few black stains on the floor. His eyes went wide in confusion and his body went stiff, suddenly another black drop fell from the direction of his face and hit the floor. He shakily put a hand to his mouth and pulled back to reveal the same blackness on his fingers, he began to shake in fear. Something was happening to him and he had no clue what it could be, was this because of the void or was it because of everything else?

“Doc?” Sans’ voice came from the other side of the door followed by a knock, “It’s time for dinner, I know you don’t like it but you gotta eat.”

No response.

“Doc?” Sans said a bit louder.

Silence.

“If this is some kinda trick, it ain't gonna work.”

Nothing.

“Gaster?” He asked, his voice breaking slightly.

Sans opened the door to see Gaster on the floor with his hand to his mouth, he was looking at the floor near Sans’ feet. Sans looked down to see black spots on the floor, he looked at Gaster only to notice that some of the same blackness was also falling from his chin. Sans ran over to Gaster in a panic, his eye glowing brighter than usual. 

“Let me see.” He said in a commanding tone, but Gaster was still too shocked to move; he just stared up at Sans. Sans grabbed his hand in a panic and yanked it away from Gaster’s mouth, blackness was leaking from Gaster’s mouth in large strands and dripping down to his chin.

“Sans?” Gaster asked shakily, “What’s happening to me?”

Sans’ eyes shot up to meet Gaster’s

“You’re changing.”

“Changing...?” Gaster asked quietly, “What do you mean?”

Sans let out a breath and looked at Gaster with a sympathetic look in his eye, “Soon you’re gonna be like everyone else.”

Gaster began to shake harder, he didn’t want to be like everyone else in the underground. Sans did his best to soothe him as his face continued to leak that awful black liquid.

**Notes for the Chapter:**

> AU-  
> Horrortale


End file.
